Namenode HA using Journal node

In this recipe, we look to configure Namenode high availability using Journal nodes, ZooKeeper, and ZooKeeper failover controller (ZKFC). This is an automatic failover, rather than the manual one discussed previously.

Getting ready

Before going through the recipes in this chapter, make sure you have two nodes that can be used as Namenodes. The following steps will guide you through the process of setting up Namenode HA using the Journal node.

The role of the Journal node is to keep the Namenodes in sync and prevent split brain. Journal nodes are distributed systems for storing edits.

How to do it...

1. Connect to the master node in the cluster. The user can start with any master node, either master1 or master2. Both of these will be used Namenodes.
2. Switch to the user hadoop.
3. Navigate to the directory where Hadoop is installed:

   /opt/cluster/hadoop/etc/hadoop
   

4. Edit core-site.xml to add the name service string instead of any specific Namenode address, as shown in the following...